An ocular cerebral impedance plethysmograph and an ocular photoelectric plethysmograph will be developed to detect and quantify arteriosclerosis involving the carotid artery. Both instruments will record arterial pulsations in anatomic regions supplied by the internal carotid artery. Analysis of these pulse recordings should reflect the degree of patency of the carotid artery. Computer assistance will be used to correlate the plethysmographic parameters with angiographic and hemodynamic data. Particular attention will be devoted to those parameters which can be measured directly from strip chart recordings, or with the aid of minimal computation circuitry.